文档介绍：Pain
Definition of pain
A signal of disease
Unpleasant sensation localized to a part of the body
rating or tissue destructive process
stabbing burning twisting tearing squeezing
Bodily or emotional reaction
terrifying nauseating sickening
panied by anxiety
Urging to escape or terminating the feeling
Both sensation and emotion
Pathophysiology
Irritating substances
bradykinins serotonin acetylchonie histamine
5-hydroxytypamine prostaglandins acid metabolites
Sensation of nerve endings:
sending through posterior root of spinal cord
cross to the other side
through spinothalamic tract, lateral medulla pons, internal capsule, spread into parietal and frontal lobe
Segmental distribution of sensation
The pain sensory system
The primary afferent nociceptor:
(初级传入伤害感受器)
A peripheral nerve (外周神经)consists of axons (轴索)of three different types of neurons (神经元):
primary sensory afferents(初级感觉传入)
motor neurons(运动神经元)
sympathetic postganglionic neurons(交感神经节后神经元)
The cell bodies of primary afferents: located in the dorsal root ganglia in the vertebral formina
Primary afferent nociceptor
Primary afferent axon bifurcates to send one process into the spinal cord and the other to innervate bodily tissue
Primary afferents are classified by their diameter, degree of myelination, and conduction velocity
A-beta
A-delta
C fiber
Primary afferent nociceptor
A-beta fiber: largest-diameter fiber, respond maximally in nerves
that innervate the skin. Normally, it does not produce pain.
A-delta fiber: 6~8 m in diameter
C fiber: 2~4m in diameter, unmyelinated
Most A-delta and C afferents respond maximally only to intense (painful) stimuli and produce pain when they are electrically stimulated; this defines them as primary afferent nociceptors (pain receptors)
Primary ponents of a typical cutaneous nerve
Sensitization (1)
When intense, repeated or prolonged stimuli are applied
if tissue is damaged or if inflammation is present
The threshold for activating primary affer